1. Field of the invention
The present invention relates to an optical fiber probe and cantilever. having a microscopic aperture, used in a scanning near-field microscope, and to a method of forming this aperture.
2. Description of the Prior Art
An optical fiber probe of a scanning near-field microscope of the related art is manufactured using the type of method described below
(1) Tip sharpening step
{circle around (1)} Hot pulling method: heat is applied to the optical fiber probe, etc., and the optical fiber is pulled in an axial direction to sharpen the tip.
{circle around (2)} Etching method: the optical probe is immersed in etching fluid, and the tip is sharpened under predetermined etching conditions.
(2) Aperture forming step
{circle around (1)} Oblique vapor deposition method: an aperture section of the extreme tip section of the sharpened probe are left behind, and a metal is vapor deposited from an oblique direction so that sections other than the aperture are covered with a metallic film.
{circle around (2)} Pressing method: After a metallic film has been vapor deposited on a section including a tip section, the tip section is pressed against a sample surface to form an aperture. With this method, the probe is brought into contact with a detector surface made of silicon utilizing shear force, while carrying out distance regulation, and after contact the tip is broken using an external. impulsive force etc. while monitoring the detector output, until a desired output is obtained.
Also, in the case where a bent type optical fiber probe is processed, a bending step is carried out between the steps (1) and (2) described above. In the bending step laser light is applied to the sharpened probe, and the optical fiber is softened by the thermal effect. At this time, the probe is bent by a surface tension effect of the softened optical fiber material.
The manufacturing steps as described above are disclosed, for example, in the near-field nanophotonics handbook, 23-28 and 42-48, optronics society. Also, the method of forming an aperture by pressing an optical fiber probe is described in a xe2x80x9cfiber probe aperture control method for near-field light microscopexe2x80x9d by Teruyama and Saiki, 46th lectures of the applied physics association, 1030.
On the other hand, with a scanning near-field microscope, a cantilever with a microscopic aperture is also used (for example, H.Zhou, A.Midha, L.Bruchhaus, G.Mills, L.Donaldson, and J. M. R.Weaver: Novel SNOM/AFM Probes by combined Micromachining and Electron-Beam Nanolithography, Preliminary Proceedings of STM ""99, 459). A cantilever with a microscopic aperture has a cantilever section and a probe formed of a silicon nitride or silicon material using a semiconductor process, a microscopic aperture is provided in the probe tip, and the microscopic aperture is made into a through hole so that a beam is focused by an objective lens onto a rear surface of the cantilever, passed through the through holes and a laser beam is introduced. The tip section is also covered with a metallic film in the cantilever having a microscopic aperture.
However, with the aperture forming method of the related art, there are the following problems.
(1) In the case of the oblique vapor deposition method, in order to make an aperture with good reproducibility, it is necessary to optimize vapor deposition conditions. This optimization requires time, and also, in the case where the probe shape is altered, it is necessary to carry out the optimization again. Further, it is not possible to avoid variations in aperture diameter, even after optimization. Once the aperture have been formed, it is impossible to correct them and defective products must be discarded.
(2) In the case of the pressing method, light output is being monitored at the tome of forming the aperture, which means that thee is the advantage that a desired aperture can be obtained. However, with the method of the related art, it is difficult to regulate the pressing force, and fine adjustment of the aperture diameter is difficult. Because of this, it is often the case that the aperture diameter becomes bigger than a desired diameter because the pressing force is to large, or the tip is damaged and the shape of the aperture becomes elliptical.
In order to solve these problems in the related art, an object of the present invention is therefore to provide an optical fiber probe and a cantilever having a microscopic aperture, capable of obtaining an aperture of a desired diameter with good reproducibility, and finely adjusting a force for plastic deformation or breaking of a tip, and a method of forming this aperture.
In order to solve the foregoing problems in the conventional art, the optical fiber probe and cantilever with a microscopic aperture of the present invention includes means for bringing a probe tip and a sample close together or into contact with each other utilizing an atomic force or shear force acting between the optical fiber probe or the. probe tip of the cantilever with a microscopic aperture, or a tunnel current or evanescent light, regulating a force on the probe tip with a physical amount of any of these as a parameter, and forming an aperture of a desired diameter at the tip section by plastic deformation or breaking of the tip section of the probe using a force received from a sample surface.